Epigeal germination

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Epigeal germination

Epigeal germination is a type of seed germination in which the cotyledons are raised above the ground level. This process is characterized by the elongation of the hypocotyl, which pushes the cotyledons upwards. Epigeal germination is commonly observed in dicotyledonous plants.

Process

During epigeal germination, the seed absorbs water and swells, causing the seed coat to rupture. The radicle emerges first, anchoring the seedling into the soil. Following this, the hypocotyl elongates and forms a hook shape to protect the delicate shoot apical meristem as it pushes through the soil. Once the hypocotyl straightens, the cotyledons are lifted above the soil surface, where they often turn green and begin photosynthesis.

Examples

Several plant species exhibit epigeal germination, including:

• Phaseolus vulgaris (common bean)
• Helianthus annuus (sunflower)
• Ricinus communis (castor bean)

Comparison with Hypogeal Germination

Epigeal germination is contrasted with hypogeal germination, where the cotyledons remain below the ground. In hypogeal germination, the epicotyl elongates instead of the hypocotyl. This difference in germination strategies can affect the plant's initial growth and development.

Advantages

Epigeal germination has several advantages:

• The cotyledons, being above ground, can perform photosynthesis, providing additional energy to the young seedling.
• The elevated cotyledons can avoid some soil-borne pathogens and pests.

Disadvantages

However, there are also disadvantages:

• The exposed cotyledons are more vulnerable to herbivores and environmental stress.
• The energy expenditure in elongating the hypocotyl can be significant.

Related Pages

• Germination
• Hypogeal germination
• Cotyledon
• Hypocotyl
• Radicle
• Seedling

See Also

• Seed dormancy
• Photosynthesis
• Plant physiology